[tip: sched/core] sched/psi: Avoid updating PSI triggers and ->rtpoll_total when there are no state changes

[tip-bot2 for Yang Yang]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     80cc1d1d5ee35701daf11725ce06d8a240588973
Gitweb:        https://git.kernel.org/tip/80cc1d1d5ee35701daf11725ce06d8a240588973
Author:        Yang Yang <yang.yang29@xxxxxxxxxx>
AuthorDate:    Tue, 10 Oct 2023 16:41:07 +08:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 11 Oct 2023 23:07:50 +02:00

sched/psi: Avoid updating PSI triggers and ->rtpoll_total when there are no state changes

When psimon wakes up and there are no state changes for ->rtpoll_states,
it's unnecessary to update triggers and ->rtpoll_total because the pressures
being monitored by the user have not changed.

This will help to slightly reduce unnecessary computations of PSI.

[ mingo: Changelog updates ]

Signed-off-by: Yang Yang <yang.yang29@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Peter Ziljstra <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/202310101641075436843@xxxxxxxxxx
---
 kernel/sched/psi.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index be853f2..79f8db0 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -704,11 +704,12 @@ static void psi_rtpoll_work(struct psi_group *group)
 	}
 
 	if (now >= group->rtpoll_next_update) {
-		update_triggers(group, now, &update_total, PSI_POLL);
-		group->rtpoll_next_update = now + group->rtpoll_min_period;
-		if (update_total)
+		if (changed_states & group->rtpoll_states) {
+			update_triggers(group, now, &update_total, PSI_POLL);
 			memcpy(group->rtpoll_total, group->total[PSI_POLL],
 				   sizeof(group->rtpoll_total));
+		}
+		group->rtpoll_next_update = now + group->rtpoll_min_period;
 	}
 
 	psi_schedule_rtpoll_work(group,